Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By addition of entire unsaturated molecules – e.g.,...
Reexamination Certificate
1999-07-16
2001-02-06
Utech, Benjamin L. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By addition of entire unsaturated molecules, e.g.,...
C585S520000, C585S521000, C585S523000
Reexamination Certificate
active
06184429
ABSTRACT:
This invention relates generally to a novel catalyst composition, comprising of an aluminum halide and a metal alkoxide belonging to group IVB, for selectively oligomerising olefins, present in a mixture of olefins, aromatics, paraffins and cycloparaffins, to polyolefins in good yields. A particular application of invention is particularly useful for oligomerisation of olefins, contained in cracked refinery distillate streams to give poly olefins, which after the steps of distillation and stabilization by hydrogenation, give oligomers suitable for use as lubricating oil base stocks.
BACKGROUND OF TIHE INVENTION
Synthetic oil base stocks having viscosities of about 4 to 30 cSt or above at 100° C. have been prepared in prior art by oligomerisation of olefins by conventional or modified Friedel-Craft catalysts. Thus by contacting the alphaolefins with boron trifluoride containing various promoters, synthetic oils suitable for lubricant use have been prepared, such as described in U.S. Pat. Nos. 4,400,565; 5,068,487 and 5,191,140. However, boron trifluoride being pulmonary irritant is fast being replaced by less hazardous catalysts like aluminum halides.
A number of aluminum halide catalyst systems have been disclosed for oligomerisation of alpha olefins to poly alpha olefins which could be used as lubricating oil base stocks possessing low pour points, higher viscosity index and good oxidation stability. U.S. Pat. No. 3,637,503 discloses the oligomerisation of alpha olefins having from 4 to 16 carbon atoms in the presence of aluminum chloride and a non-polymerizing hydrocarbon diluent. Similarly aluminum chloride alone or along with organic promoters have been used to oligomerise alpha olefins either pure or in presence of a non-oligomerising hydrocarbon diluent. See for example U.S. Pat. Nos. 5,196,635; 5,136,118; 4,107,080; 4,219,691 and 4,031,159. It is also known in the related field the possibility of oligomerising olefins in which the double bond is statistically distributed along the entire carbon chains. Thus U.S. Pat. No. 4,167,534 discloses tile oligomerisation of olefins obtained from a PACOL-OLEX process, by contacting with aluminum chloride to obtain oligomers which after distillation and catalytic hydrogenation gave the lubricating oil. Even though the feed stock for oligomerisation was predominantly olefinic (up to 95%), the yield and the viscosity of the resulting oligomer were very poor.
However, all these processes pertain to oligomerisation of either pure or mixtures of pure alpha-olefins, and suprisingly there are no reports on the utilisation of linear olefins contained in refinery streams, for the production of synthetic lubricant base stocks. Various refinery produced cracked distillate streams, particularly from Coker and FCC units, are quite rich in desired alpha-olefins, which can be selectively concentrated by the process of urea adduction.
A major deficiency with the conventional Friedel-Craft catalysts is their inability to selectively oligomerise olefins in the presence of other unsaturated compounds like aromatics. However, aluminum chloride alone or with promoters is known to promote the alkylation of aromatics with olefins, when applied to cracked refinery distillate streams which contained appreciable amounts of aromatics alongwith olefins. The oligomeric product thus obtained contain alkylated aromatics, which made these products unsuitable for use as lubricating oils, because of very poor oxidation stability. No prior art method either discloses or teaches any catalyst system which can selectively oligomerise olefins to poly olefins in the presence of aromatics. Consequently, it is infact impossible to prepare an olefin oligomer having high viscosity index and high oxidation stability which could be qualified for such uses as gas turbine oil, hydraulic fluid for air crafts, crankcase oils, etc by selective oligomerisation of olefins present in the cracked refinery stream distillates which also contain aromatics, besides paraffins and cycloparaffins, by use of Friedel-Craft catalyst systems disclosed in the prior art. The present invention provides for a catalyst composition for preparation of olefin oligomers suitable for use as lubricating oils by selective oligomerisation of olefins, contained in cracked refinery stream distillates, which have been processed through a step of urea adduction.
OBJECTS OF THE INVENTION
An object of the present invention is to propose a catalyst composition for selectively oligomerising olefins present in cracked refinery stream distillates which comprised of olefins, aromatics, paraffins and cycloparaffins having 8 to 20 carbon atoms.
A further object of this invention is to propose a catalyst composition which provides higher conversion of olefins present in the cracked refinery stream distillates, processed through a step of urea adduction and containing upto 5% aromatics.
Yet another object of the present invention is to propose a catalyst system for selective oligomerisation of olefins contained in refinery distillate streams to produce oligomers having high viscosity index, low pour point and higher oxidation stability for their use as base stocks in synthetic lubricants.
DESCRIPTION OF THE INVENTION
According to this invention, there is provided a catalyst composition for use in oligomerisation of olefins, contained in refinery distillate streams, comprising an aluminum halide component and a catalyst component selected from an alkoxide of a metal belonging to group IVB.
Further according to this invention, there is provided a process for preparing polyalphaolefin synthetic lubricants, comprising in oligomerisation of olefins of cracked refinery streams, having 8 to 20 carbon atoms, in the presence of corresponding paraffins, naphthenes and aromatics, in the presence of a catalyst consisting of an aluminum halide and group IVB transition metal alkoxide, to provide an olefin oligomer, having viscosity of 7-30 cSt at 100° C.
The catalyst composition used in the oligomerisation process of the present invention is a two component system comprising (A) an aluminum halide component and (B) a second catalyst component which is a alkoxide of a metal belonging to group IVB. The aluminum halides which are suitable for use in the catalyst system of the present invention include aluminum fluoride, aluminum chloride, aluminum bromide and aluminum iodide and mixture thereof. The preferred aluminum halide is aluminum chloride. The second component of the proposed oligomerisation catalyst system comprises a metal alkoxide having the general formula M(OR)
4
wherein M is selected from the group of metals belonging to group IV B of the periodic table and R is alkyl of 1 to 12 carbon atoms or alkylaryl having alkyl chain of 1-12 carbon atoms. Preferably R is lower alkyl of 2 to 6 carbon atoms.
A preferred catalyst composition is obtained when metal alkoxide is a titanium alkoxide. A particularity preferred catalyst composition contains aluminum chloride and a titanium alkoxide such as titanium tetra isopropoxide or titanium tetra n-butoxide.
The molar ratio of aluminum halide to the transition metal alkoxide is important for optimum catalyst activity and for product quality in terms of viscosity and pour points. Generally the molar ratio of aluminum to transition metal is from 100:1 to 4:1, preferably about 60:1 to 10:1. The amount of aluminum halide catalyst can vary and amounts of from about 0.5 to 10 weight percent based on the amount of olefin is preferred. The specially preferred amount of aluminum halide is from 1 to 4 weight percent of olefins.
The raw material suitable for the present catalyst composition can consist of alpha olefins having number of carbon atoms between 8 and 24, n-olefins having the double bond statistically distributed along the entire carbon chain and having number of carbon atoms between 8 and 24, and the mixtures of n-olefins and alpha olefins in any ratio. The proposed catalyst composition is also suitable for raw materials obtained from PACOL process or from wax cracking and containing a mix
Bhatnagar Akhilesh Kumar
Ghosh Sobhan
Mohan Rai Madan
Ray Sabyasachi Sinha
Sarin Rakesh
Dang Thuan D.
Spencer George H.
The Indian Oil Corporation Ltd.
Utech Benjamin L.
Venable
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